Robot tool changer and overload device

ABSTRACT

A robot tool changer and overload device has first and second separable plates adapted to be respectively connected to a robot arm and to an end of arm tooling device (EOAT) for the robot; a magnet is connected to one of the plates and a steel insert is connected to the other of the plates for providing a magnetic attraction therebetween for holding the first and second plates together; a pair of frustoconical bearing surfaces are formed on the first and second plates at an angle and a depth to interconnect the plates during normal operation and operative to produce pivotal release movement between the plates when an overload force is applied thereto; a flange on one of the plates is adapted to be removably received within a tool cage to cooperate with structure for applying a pneumatic release force between the first and second plates to allow separation therebetween along a Z axis without imposing an overlaod force on the robot arm.

TECHNICAL FIELD

This invention relates to overload devices for releasing an end of armtooling device (EOAT) from a robot arm to prevent imposition ofoverloads on the robot arm, and more particularly, to such devicesincluding a robot tool changer plate adapted to be removably receivedwithin a tool cage.

BACKGROUND OF THE INVENTION

Robot tool changers are known which include a first plate that isadapted to be connected to a robot arm and a second plate that isadapted to be connected to an end of the arm tool for the robot. In sucharrangements, a coupling system is provided between the first and secondplates for aligning the plates and connecting them together for securingthe end of the arm tool to the robot arm and to provide a strong jointbetween the first and second plates during operation of the robot. Anexample of such a tool changer is set forth in U.S. Pat. No. 4,793,053which is assigned to the assignee of the subject application.

In the '053 patent, a pair of deep draft frustoconical annular surfacesare provided therebetween to provide a strong non-tilt release jointbetween the first and second plates. The frustoconical surfaces have adepth and a bearing surface which prevents separation of the first andsecond plates other than along the Z axis or longitudinal axes of theconnected plates.

Other devices are provided between the robot arm and an EOAT to preventan overload force from being imposed on the robot arm during itsoperation. One such system is set forth U.S. Pat. No. 4,860,864 assignedto an assignee common to that of the present application.

In the '405 application, a magnet and a steel plate are connectedbetween first and second plates of the device to maintain a magneticattraction therebetween to complete a joint between a robot arm and anend of arm tool device. The magnetic force is broken to decouple the endof arm tool from the robot arm by providing cam surfaces on one of theplates and a tapered nest configuration on the opposite plate to causethe magnet to be separated from the steel plate insert on the other ofthe plates when one of the plates is moved torsionally along at leastone of three coordinate linear axes when a load applied to the end ofthe arm device exceeds an overload force condition on the robot arm.

While the aforesaid robot tool changer of the '053 patent and the breakaway connection of the '405 application are suitable for their intendedpurposes, neither the tool changer device nor the break away device havethe capability of performing the functional purpose of the other.

SUMMARY OF THE INVENTION AND ADVANTAGES

Accordingly, one feature of the present invention is to provide aunitary device between a robot and an EOAT combining both tool changerand overload release functions in a unitary device having a single pairof separable plates.

Another feature is to provide such a unitary device having separableplates held together by magnet means and including break away surfacesthereon to allow the first and second plates to pivot apart upon theoccurrence of an overload condition on the EOAT that might damage therobot arm.

Still another feature is to provide a pneumatic release system betweenthe first and second plates operative to produce separation therebetweenindependently of the imposition of any overload moment thereon to allowmovement of the first plate from the second plate in a Z axis when anEOAT is nested in its tool crib.

Another feature of the present invention is to provide an improved robottool changer and overload device having first and second platesrespectively connected to a robot and an EOAT and including a magnettherebetween to produce a magnetic force for holding &he first andsecond plates together and wherein the first and second plates havecoacting frustoconical surfaces thereon that define a pivot pointcompletely around the circumference of the joined plates for separatingthe plates when a moment is applied therebetween of a magnitude tooverload the robot arm.

Still another feature of the present invention is to provide the toolchanger and overload device of the preceding object wherein thefrustoconical surfaces have a depth and an angle selected to producecomplete separation between the first and second plates when an overloadmoment is applied thereto; and wherein means are provided topneumatically release the first and second plates in a Z axis withoutimposing any excessive load on the robot arm when the device issupported in a tool crib nest.

It is another object of the present invention to provide a improvedrobot tool changer and overload device having first and second platesrespectively connectible to a robot arm and to an EOAT and includingmagnet means for producing a magnetic force for holding the first andsecond plates together during normal robot operation, and further,including means for forming coacting support surfaces on each of thefirst and second plates that form a mechanical joint between the firstand second plates under normal robot operation and wherein the coactingsurfaces have an angle inclined with respect to the Z axes of the firstand second plates to produce separation of the first and second platesby pivotal movement therebetween at the annular outer edge of thesupport surfaces when an overload is applied to one of the plates.

Still another object of the present invention is to provide the robottool changer and overload device of the preceding object whereinpneumatic release means are provided between the first and second platesfor producing separation of the plates without pivotal movementtherebetween.

Still another object of the present invention is to provide an improvedrobot tool changer and overload device for controlling the separationbetween first and second plates respectively connected to a robot armand to an EOAT wherein each of the first and second plates are connectedtogether by a frustoconical surface thereon having an angle ofinclination with respect to the Z axes of the first and second platesand a depth which will allow pivotal release of the first and secondplates with respect to a magnet for holding the plates together when anoverload condition is imposed between the first and second plates andwherein a pair of opposed surfaces are formed on the first and secondplates for receiving a pressure release medium therebetween so as toovercome the attractive force of the magnet to produce separation of thefirst and second plates when one of the plates is captured in the nestof a tool crib to thereby change tools on the first plate withoutimposing a damaging load on the robot arm.

Still another object of the present invention is to provide the robottool changer and overload device of the preceding object and wherein therelease surfaces produce a pneumatic force in the direction of the Zaxes of the first and second plate to produce a separation forcetherebetween of a magnitude in excess of that of said magnet so as toallow a robot arm to remove one of the plates from a plate nested withinthe tool crib without imposing an overload on the robot arm.

Other objects, desires and advantages of the invention will become moreapparent to those skilled in the art as the nature of the invention isbetter understood from the accompanying drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of the present invention shown nestedin a tool crib shown in cross-section;

FIG. 2 is a top elevational view of the present invention looking in thedirection of the arrows 2--2 in FIG. 1;

FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 2,looking in the direction of the arrows;

FIG. 4 is a sectional view taken along the line 4--4 of FIG. 1, lookingin the direction of the arrow;

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 2, lookingin the direction of the arrows; and

FIG. 6 is a view like FIG. 3 showing an EOAT plate of the presentinvention in a tilted, breakaway position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, a diagrammatically shown robot 10 isillustrated having a robot arm 12 with an end plate 14 connected to oneend of a robot tool changer and overload device 15 constructed inaccordance with the present invention.

The opposite end of the robot tool changer and overload device 15 isconnected to a plate 16 on an end of arm tooling device or EOAT 18 shownin outline form. In accordance with certain principles of the presentinvention, the robot tool changer and overload device 15 has a mountingflange 20 for removably supporting the device 15 in a support nest 22 ofa tool crib 24. While the tool crib 24 shows only a single nest, itshould be understood that in practice such cribs comprise a plurality ofsuch nests. Each nest 22 is formed by a pair of spaced rails 26, 28forming a support track having a depth substantially equal to that ofthe mounting flange 20 and capturing the mounting flange 20 to preventit from being moved along the Z axis of the device 15. The mountingflange 20 is movable laterally of the tool crib 24 through side opening30 therein for removing a selected EOAT from the tool crib 24. Theselection of a particular EOAT will depend upon the processing sequenceto be conducted on a workpiece or workpieces by the robot 10.

In accordance with certain principles of the present invention, therobot tool changer and overload device 15 includes an upper plate 32 anda lower plate 34. As shown in FIGS. 3 and 4, the upper plate 32 has acircular opening 35 therein in which is fitted a support plate 36. Thesupport plate 36 is oriented with respect to air supply and electricalconnections (to be described) by a dowel pin 37c fit between plates 32and 36. The upper plate 32 also carries a rectangular permanent magnet38 at end flanges 38a thereof. The permanent magnet 38 is connected tothe inner surface 32a of the upper plate by suitable fastening means.The permanent magnet cell 38 is a MAGNEQUENCH magnetic cell of a typemanufactured by General Motors Corporation. A more detailed explanationof such magnets is set forth in U.S. Pat. No. 4,496,395 with a commonassignee to that of the present application.

The permanent magnet 38 is operatively associated with a steel insert 42which is connected to the inner surface 34a of the lower plate 34 byscrews 43 threadably received by internally threaded inserts 45 in lowerplate 34.

When the permanent magnet 38 is located in a predetermined spacedrelationship to the steel insert 42, it will produce a magneticattraction between the upper and lower plates 32, 34 to cause them to bejoined. More particularly, the upper plate 32 includes a frustoconicalsurface 44 thereon that defines a nest to receive a congruentfrustoconical surface 46 on the lower plate 34. The frustoconicalsurfaces 44, 46 are located in overlapping engagement with one another,as shown in FIG. 5, when the upper and lower plates 32, 34 aremagnetically connected to one another. The surfaces 44, 46 define abearing surface for supporting normal loading on the robot arm 12 andthe EOAT 18.

In accordance with certain principles of the present invention, thefrustoconical surfaces 44, 46 have a depth which will enable one side ofthe lower plate 34 to be tilted downwardly with respect to the otherside of the upper plate 32, as shown in FIG. 6, to release the upper andlower plates 32, 34 so as to be broken apart when an overload force isapplied therebetween.

The frustoconical surfaces 44, 46 have an angle of inclination 48 whichis formed as an acute angle to the direction of Z axis 50 of the device15 as shown in FIG. 6. The angle of inclination and the depth D of thefrustoconical surfaces 44, 46 combine to assure clean breakaway when anoverload release moment 52 is applied by a force located on the device15 in the Z axis direction along either the X or Y axis.

Such release moment 52 will produce the tilting movement shown betweenthe nested, normal operating position of FIG. 5 and the tilt breakawayposition of FIG. 6. In order to assume the tilt breakaway position, theoverload release moment 52 must produce a relative separation forcebetween the upper plate and the lower plate 32, 34 that exceeds themagnetic attraction force between the permanent magnet 38 and the steelinsert 42. Once this occurs, at any point around the circumference ofthe device 15, the lower plate 34 will assume the breakaway positionshown in FIG. 6 at which point the attraction force between the upperand lower plates 32, 34 is instantaneously eliminated so as to assurethat the overload force will not be transferred to the robot arm 12 in amanner that will cause the robot 10 to be damaged. The plates 32, 34 canbe completely separated. Alternatively, they can be tethered so that theEOAT remains loosely connected to the robot arm 12 following separation.

In the illustrated arrangement, the frustoconical surfaces 44, 46 areformed completely circumferentially of the respective plates 32, 34. Thecircumferential form allows a universal release action in any directionbetween the plates to protect against overloads in any robot operationwherein it is desired to protect the robot arm 12 from forces imposed onthe EOAT during the operation of the robot.

In accordance with other principles of the present invention, thesupport plate 36 on the upper plate 32 has a surface 54 arrangedperpendicular to the Z axis 50. The lower plate 34 has a surface 56arranged perpendicularly to the Z axis and in juxtaposed opposition tothe surface 54 when the plates 32, 34 are connected.

The opposed surfaces 54, 56 are located in sealing engagement with oneanother when the upper and lower plates 32, 34 are interlocked as shownin FIG. 5. The surface 56 includes an annular channel 58 therein whichis covered by an annular segment 60 of the surface 54. The annularchannel 58 has high pressure air directed therethrough through a tappedinlet 62 in the upper plate 32, thence through an axial passage 64 inthe support plate 36.

The tapped opening 62 is adapted to be connected to an air supplyconduit 66 having a control valve 68 therein for selectively opening andclosing the supply line 68 for directing air from a pressure source 70on the robot 10. The robot pressure source 70 also supplies thepneumatic air pressure to the EOAT. The supply for such EOAT operationis through a tapped opening 72 in the upper plate 32, thence throughdrilled holes 74, 76, 78 and 80. The drilled hole 78 is sealed at theupper and lower end of the support plate 36 by O-rings 82, 84. Thedrilled hole 80 connects to air ports 86,86', one of which is shown at86 in FIG. 5, for supplying pressurized air to the EOAT. The air supplypath to port 86' (in FIG. 2) is like that previously described. The likecomponents seen in FIG. 2 are identified with like reference numeralsprimed.

Air flow through the valve 70 is under the control of a robot controller88 which is operative to simultaneously open the valve 70 and to drive arobot drive 90 to move the robot arm 12 in the Z axis direction of thedevice 15 when it is desired to release or connect the robot from or toan EOAT in tool crib 24.

As shown in FIG. 4, electric power supply for the EOAT is supplied bypin contact sets 92, 94 (four pin contacts in each set). The contact set92 has female pins and is held in the plate 32 by a set screw 96. Thecontact set 94 has male pins held in place on plate 32 by a set screw98. Terminals 100, 102 on the contact sets 92, 94, respectively, areadapted to be connected respectively to power supply 91 and to the EOAT.Power supply to the EOAT is controlled by controller 88.

More particularly, by virtue of the aforedescribed controller 88,release of an EOAT from the robot is as follows. The device 15 ismanipulated so as to move laterally through the side openings 30 into anested relationship within a given one of a plurality of nests 22 in amulti-nest tool crib 24. At this point, in order to carry out a toolchanger release operation in accordance with the present invention, therobot controller 88 will simultaneously open the valve 70 and will drivethe robot drive 90 so as to cause the robot arm 12 to move only in a Zaxis direction. As the arm 12 moves vertically, a pressure is directedinto the annular channel 58. The pneumatic pressure will be imposed onthe annular segment 60 of the surface 54 to produce a release forcebetween the upper and lower plates 32, 34 of a magnitude to overcome themagnetic attractive force between the permanent magnet 38 and the steelinsert 42. Accordingly, the robot arm 12 is separated from the EOAT thatis supported by the mounting flange 20 in the tool crib. The separationoccurs without imposing any overload or damaging force on either therobot arm 12 or the robot 10.

Tool change connection of the robot arm 12 to an EOAT is accomplished byreversing the aforedescribed release operation. Specifically, the upperplate 32 is directed along a Z axis until the magnet 38 is attracted tothe steel insert 42 of a lower plate 34 on the EOAT which is to beselected from the tool crib 24. The valve 70 is closed so that there isno pneumatic release force imposed between juxtaposed surfaces 54, 56.Once the plates 32, 34 are coupled, the device 15 is moved laterallythrough the opening 30 so as to be removed from the crib 24 inpreparation for a desired robot controlled processing sequence for theEOAT.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be described otherwise than as specifically set forth herein.

What is claimed is:
 1. A robot tool changer and overload device having arobot connectible first plate and an end of arm tooling deviceconnectible second plate and a magnet means for producing a magneticforce for holding the first and second plates together characterizedby:means forming coacting inclined surface means on said first andsecond plates defining a pivot point for separation of said first andsecond plates when a moment is applied therebetween of a magnitude toovercome the magnet force therebetween; said coacting inclined surfacemeans having a depth and an included inclination angle formed acutelywith respect to the longitudinal axis through said first and secondplates to produce pivoting of one of said first and second platesthrough an acute angle corresponding substantially to that of saidincluded angle to release said first and second plates when an overloadoccurs so as to release all force on the robot by complete separation ofsaid first and second plates; and release means for imposing a releaseforce between said first and second plates to produce separation betweensaid first and second plates independently of the imposition of anyoverload moment thereon to allow movement of said first plate withrespect to said second plate in a Z axis direction without imposing anyload on the robot during such movement.
 2. The robot tool changer andoverload device of claim 1, further characterized by said surface meansincluding a circular surface on said first plate having a depth andangle that will produce full separation of the second plate from thefirst plate simultaneously with the overload moment overcoming themagnetic force of said magnet means.
 3. The robot tool changer andoverload device of claim 1, further characterized by said surface meansincluding a first circular inclined surface defining a female nest onsaid first plate formed circumferentially of said magnet means insurrounding relationship therewith and said surface means including asecond circular inclined surface on said second plate forming a maleinsert locatable within said female nest so as to cause said first andsecond inclined surfaces to couple said first and second platestogether.
 4. The robot tool changer and overload device of claim 1,further characterized by said release means including opposed surfaceson said first and second plates and means for directing pressure mediumbetween said opposed surfaces for overcoming the attractive force ofsaid magnet means.
 5. The robot tool changer and overload device ofclaim 2, further characterized by said inclined surfaces having a depthand an angle of inclination which will allow complete release of saidfirst plate from said second plate by universal pivotal movementtherebetween in response to imposition of a relative moment between saidfirst and second plates produced by an overload force imposed thereon.6. The robot tool changer and overload device of claim 3, furthercharacterized by said inclined surfaces having a depth and an angle ofinclination and a circumferential extent which will allow completerelease of said first plate from said second plate by pivotal movementat any point along the full circumference of said inclined surfacestherebetween in response to imposition of a relative moment between saidfirst and second plates produced by an overload force imposed thereon.7. The robot tool changer and overload device of claim 4, furthercharacterized by said first plate having an air passage therein adaptedto be connected to a source of pressurized air and extending throughsaid first plate; and means forming an annular channel in said secondplate communicating with said air passage and facing said first plateand sealed with respect thereto when said first and second plates areheld together by said magnet means so as to produce a Z axis pneumaticrelease force to overcome the magnetic attraction of said magnet meanswhen pressurized air is directed into said annular channel.
 8. The robottool changer and overload device of claim 1, wherein said robot has amotor for moving said first plate away from said second plate along theZ axis, said robot tool changer and overload device furthercharacterized by said pneumatic release means including a source of airpressure and valve means for controlling pressurization of saidpneumatic release means, and said;means on said second plate forsupporting a tool in a tool crib against separation therefrom in a axialdirection and for separation therefrom in a direction laterally of theaxial direction; and controller means to signal said robot for movementof said first plate in the axial direction away from said second plateand to activate said valve means to condition said release means forovercoming the magnetic force of said magnet means so as to change atool from a robot without imposing a damaging load on a robot arm. 9.The robot tool changer and overload device of claim 8, furthercharacterized by said release means including opposed surfaces on saidfirst and second plates and means for directing pressure fluid betweensaid opposed surfaces for overcoming the magnetic force of said magnetmeans.
 10. The robot tool changer and overload device of claim 9,further characterized by said first plate having an air passage thereinadapted to be connected to a source of pressurized air and extendingthrough said first plate; and means forming an annular channel in saidsecond plate communicating with said air passage and facing said firstplate and sealed with respect thereto when said first and second platesare held together by said magnet means so as to produce a Z axispneumatic release force to overcome the magnetic attraction of saidmagnet means when pressurized air is directed into said annular channel.